Classful addressing:In the classful addressing system all the IP addresses that are available are divided into the five classes A,B,C,D and E, in which class A,B and C address are frequently used because class D is for Multicast and is rarely used and class E is reserved and is not currently used.Each of the IP address belongs to a particular class that's why they are classful addresses.Earlier this addressing system did not have any name,but when classless addressing system came into existence then it is named as Classful addressing system.The main disadvantage of classful addressing is that it limited the flexibility and number of addresses that can be assigned to any device.One of the major disadvantage of classful addressing is that it does not send subnet information but it will send the complete network address. The router will supply its own subnet mask based on its locally configured subnets. As long as you have the same subnet mask and the network is contiguous, you can use subnets of a classful network address.

Classless Addressing:Classless addressing system is also known as CIDR(Classless Inter-Domain Routing).Classless addressing is a way to allocate and specify the Internet addresses used in inter-domain routing more flexibly than with the original system of Internet Protocol (IP) address classes.What happened in classful addressing is that if any company needs more than 254 host machines but far fewer than the 65,533 host addresses then the only option for the company is to take the class B address.Now suppose company needs only 1000 IP addresses for its host computers then in this (65533-1000=64533) IP addresses get wasted.For this reason, the Internet was, until the arrival of CIDR, running out of address space much more quickly than necessary. CIDR effectively solved the problem by providing a new and more flexible way to specify network addresses in routers.A CIDR network address looks like this:

192.30.250.00/15

The "192.30.250.00" is the network address itself and the "15" says that the first 15 bits are the network part of the address, leaving the last 17 bits for specific host addresses.One more advantage of classless addressing is that classless protocol sends subnet information. This allows you to create discontiguous networks with any given classful network address.

(i) Show your IP address and subnet mask

To use the ipconfig utility, go to the Start button. Select Run.

Enter command into the Open box and click OK. This will open the MS-DOS (Command) Prompt window.C:\WINDOWS\Desktop>Enter ipconfig and press Enter. You should see something similar to the output below.

and you will convert the address as the individual number like first convert 192 the 168. and so on and after that you will write in the form of binary of 192 then a dot"."and then next binary of 168 and then dot and so on